i really want to get some traits on all my epic and legendaries and yet when it comes to get runic traitstones it feels like they are impossible to find
is there a trick to it? like a challenge that’s really easy to clear for easy stones or something like that? i heard good thing about khetar when it comes to true damage for example
The types of stones you need will determine where you need to do the challenges. There is a thread on this forum that tells you what kingdoms give which stones. The only thing is it is very tiresome farming stones so be prepared for numerous repeats of the same challenge. Other players have adopted the practice of saving up glory to buy the 400 pack that is offered each week to get them that way but you’re at the whim of the dev’s as to what stones are being offered. You can get a good collection of minors and majors by doing lots and lots of pvps too.
Good luck with the grind. 
i know that the kind of traitstones is related to kingdom, i was asking if there were challenges that were particulary easy to clear over and over in order to score easy traitstones
or maybe a unit that has both an AOE attack and the fast trait or stuff like that
It comes down to personal preference for the challenges in the kingdom you’re targeting. Like, I’ll avoid Agile troops.
You can look to either use your fastest kill team, or a soul farming kill team.
The true damage - Khetar is the trick that one skull match was enough to kill a unit with the true damage, so you could clear the challenges very quickly.
In Khaziel there is a challenge called The Grudge which has a Fortress Gate as the first troop. There is another one with this set up in Broken Spire with FG in first position called Fortress Seige. The benefit with these setups is with the gate in first position with 0 attack you don’t have to worry about skulls being fired off at you. The only concern is you have to try not to fire skulls yourself and take out the wall. Just remember doing these repeats only gives the traitstones offered from each of the kingdoms (Khaziel - Earth and Arcane Deep / Broken Spire - Earth and Water and Arcane Shield).
My soul farming team is Valkyrie - Alchemist - Sunweaver - Griffon Knight. With Celestial armor and on normal difficulty I fire Val off 4 times and get the max of souls. But if you don’t have some of those the team I started with was Hero with Crude club - Deep Borer - Valkyrie - Alchemist. DB feeds Alchemist which feeds Valk which feeds DB.
I hope this is more helpful. I’ve pretty much given up on traitstone farming myself. I buy them in the glory packs.
i have alchemist, valk, valk, hero with soul sword (its blue and yellow). Since i have lots of troops to lvl up, i grid souls in the area that im trying to get arcanes. so for the divion field, i did the master because with only 1 agility guy and exploders, i could usually control the board on warlord 2.